1. Field of the Invention
This invention generally relates to a wall-mountable wiring installation and, more particularly, to a so-called boxless wiring device of the type particularly suitable for installation on and within a wall of a building such as a home, a mobile home or a factory-manufactured prefabricated home.
2. Description of the Prior Art
It is well known to install an electrical junction metallic box within an opening in a wall or the like, and thereupon to mount an electrical device, such as a duplex receptacle or a wall switch, on the box. The conventional duplex receptacle comprises a plastic body member having a pair of plug-receiving outlets arranged adjacent each other, each outlet being adapted to mate with either a 120 v or 220 v electrical plug having either two or three blades. The conventional receptacle has screw terminals on either side thereof to receive the bared ends of individual conductors of an electrical cable routed to the junction box. The conventional receptacle also has mounting ears at either end thereof and to which assembly screws are used to mount the receptacle to the junction box. A separate face plate having openings through which the electrical outlets extend is thereafter fastened with one or more screws to the receptacle or switch, not only for esthetic, but also for safety, purposes.
Although generally satisfactory for its intended purpose, the aforementioned wiring installation has not proven to be altogether satisfactory in terms of the lengthy time, large expense and inconvenience associated with, among other things, properly orienting the junction box, both vertically and horizontally, within the wall; assembling the junction box, receptacle and face plate as a unitary structure; properly preparing the electrical cable by severing the cable and routing the same to the box; and stripping the cable insulation and connecting the exposed conductors of the cable to an associated screw terminal on the receptacle or switch.
In an attempt to avoid the drawbacks associated with using a junction box, the prior art has also proposed so-called "boxless" wiring installations in which no metallic junction box is used. Such boxless installations are disclosed, for example, in U.S. Pat. Nos. 3,951,489; 3,951,502; 3,957,336 and 3,966,152, in which an electrical structure comprised of a duplex electrical receptacle is integrally formed with a face plate. A cover is mounted at the rear of the receptacle and bounds a single interior compartment to which an electrical cable is routed. Electrical contacts within the compartment engage the conductors in the cable and also engage the prongs of a plug inserted into the outlets of the receptacle. The receptacle with the cover mounted thereon is then clamped to the wall by turning wall-clamping screws and drawing swing-out wall clamps into clamping engagement with the rear face of the wall. The wall-mounting screws extend through the integral face plate, thereby exposing their heads and contributing to a non-finished, unesthetic appearance. The prior art also has proposed boxless structures in which the face plate is separate from the receptacle, with the face plate being separately mounted by means of screws to, or snapping onto, the receptacle.
Although the known boxless wiring installations do eliminate the need for the conventional junction box, and do reduce the high labor content involved in installing, cutting, stripping and wiring the individual conductors of an electrical cable, they still possess certain drawbacks. For example, one serious drawback is that, should a duplex receptacle or wall switch fail in the field, it cannot be readily replaced because special tools are required to clamp the cover to make the insulation displacing terminations on the receptacle. An electrician is usually called since the interior compartment of the wiring structure contains electrically-alive wires. The normal procedure is to replace a failed boxless installation with a conventional junction box and the appropriate electrical device.
Another serious drawback is that the installer of the known boxless wiring installations must remove all of the outer insulation of the cable, as well as all of the paper filler in the case of romex cable. This is very time consuming, but necessary because the interior electrical contacts located within the interior compartment of the duplex receptacle are in the immediate vicinity of the paper filler and, when an electrical plug is removed under load, the possibility of arcing between the interior electrical contacts can cause the paper filler to ignite, thereby representing a serious safety hazard.
Another problem associated with prior boxless wiring installations is that plastic barriers must be cut away or broken off from the walls bounding the interior compartment in order to allow for a through cable, or more than one cable, to be inserted therein. There are several possible variations in the number of cables to be routed to and terminated in the compartment. There could be one cable in, one cable in and one cable out, two cables in and one cable out, or two cables in and two cables out. Since all unused cable openings must be covered, and since there is a minimum of one cable and a maximum of four cables to be wired, the prior art boxless installations provided one constantly-open cable opening, and the remaining three cable openings were covered by the aforementioned plastic barriers. The cutting away or breaking off of one or more barriers is not only time-consuming for the installer, but also is messy.
Yet another problem associated with prior art boxless installations relates to the swing-out clamps which are used to secure the installation onto the wall. The known swing-out clamps have a clamping surface area which, if too small, tends to crush into the wall, thereby reducing the security of the installation. Also, the known clamps can, and often do, hang up on obstructions located behind the wall, on the cable itself or on displaced sections of the wall, so that the clamps sometimes cannot freely swing out and be clamped against the rear face of the wall. This problem cannot be overcome when the known boxless installations are in position on the wall and, hence, it is necessary for the installer to remove the boxless installation, cut or move the obstruction away from the swing-out clamps and, in some cases, to repeat this back-and-forth repositioning of the boxless installation on the wall, alternated with removing or cutting away any obstructions. This back-and-forth repositioning is a very time-consuming task, and represents a significant expense in terms of assembly cost.